Cong Wang wrote:
> From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
>
> We do not have to lock the sock to avoid losing sk_socket,
> instead we can purge all the ingress queues when we close
> the socket. Sending or receiving packets after orphaning
> socket makes no sense.
>
> We do purge these queues when psock refcnt reaches zero but
> here we want to purge them explicitly in sock_map_close().
> There are also some nasty race conditions on testing bit
> SK_PSOCK_TX_ENABLED and queuing/canceling the psock work,
> we can expand psock->ingress_lock a bit to protect them too.
>
> Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Cc: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
> Cc: Lorenz Bauer <lmb@xxxxxxxxxxxxxx>
> Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
> ---
> include/linux/skmsg.h | 1 +
> net/core/skmsg.c | 50 +++++++++++++++++++++++++++++++------------
> net/core/sock_map.c | 1 +
> 3 files changed, 38 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
> index f2d45a73b2b2..0f5e663f6c7f 100644
> --- a/include/linux/skmsg.h
> +++ b/include/linux/skmsg.h
> @@ -347,6 +347,7 @@ static inline void sk_psock_report_error(struct sk_psock *psock, int err)
> }
Overall looks good, comment/question below.
>
> #if IS_ENABLED(CONFIG_BPF_STREAM_PARSER)
> int sk_psock_init_strp(struct sock *sk, struct sk_psock *psock);
> diff --git a/net/core/skmsg.c b/net/core/skmsg.c
> index 305dddc51857..d0a227b0f672 100644
> --- a/net/core/skmsg.c
> +++ b/net/core/skmsg.c
> @@ -497,7 +497,7 @@ static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,
> if (!ingress) {
> if (!sock_writeable(psock->sk))
> return -EAGAIN;
> - return skb_send_sock_locked(psock->sk, skb, off, len);
> + return skb_send_sock(psock->sk, skb, off, len);
> }
> return sk_psock_skb_ingress(psock, skb);
> }
> @@ -511,8 +511,6 @@ static void sk_psock_backlog(struct work_struct *work)
> u32 len, off;
> int ret;
>
> - /* Lock sock to avoid losing sk_socket during loop. */
> - lock_sock(psock->sk);
> if (state->skb) {
> skb = state->skb;
> len = state->len;
> @@ -529,7 +527,7 @@ static void sk_psock_backlog(struct work_struct *work)
> skb_bpf_redirect_clear(skb);
> do {
> ret = -EIO;
> - if (likely(psock->sk->sk_socket))
> + if (!sock_flag(psock->sk, SOCK_DEAD))
> ret = sk_psock_handle_skb(psock, skb, off,
> len, ingress);
> if (ret <= 0) {
> @@ -537,13 +535,13 @@ static void sk_psock_backlog(struct work_struct *work)
> state->skb = skb;
> state->len = len;
> state->off = off;
> - goto end;
> + return;
Unrelated to your series I'll add it to my queue of fixes, but I think we
leak state->skb on teardown.
> }
> /* Hard errors break pipe and stop xmit. */
> sk_psock_report_error(psock, ret ? -ret : EPIPE);
> sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED);
> kfree_skb(skb);
> - goto end;
> + return;
> }
> off += ret;
> len -= ret;
> @@ -552,8 +550,6 @@ static void sk_psock_backlog(struct work_struct *work)
> if (!ingress)
> kfree_skb(skb);
> }
> -end:
> - release_sock(psock->sk);
> }
>
> struct sk_psock *sk_psock_init(struct sock *sk, int node)
> @@ -631,7 +627,7 @@ static void __sk_psock_purge_ingress_msg(struct sk_psock *psock)
> }
> }
>
> -static void sk_psock_zap_ingress(struct sk_psock *psock)
> +static void __sk_psock_zap_ingress(struct sk_psock *psock)
> {
> struct sk_buff *skb;
>
> @@ -639,8 +635,13 @@ static void sk_psock_zap_ingress(struct sk_psock *psock)
> skb_bpf_redirect_clear(skb);
> kfree_skb(skb);
> }
> - spin_lock_bh(&psock->ingress_lock);
> __sk_psock_purge_ingress_msg(psock);
> +}
> +
> +static void sk_psock_zap_ingress(struct sk_psock *psock)
> +{
> + spin_lock_bh(&psock->ingress_lock);
> + __sk_psock_zap_ingress(psock);
> spin_unlock_bh(&psock->ingress_lock);
I'm wondering about callers of sk_psock_zap_ingress() and why the lock is
needed here. We have two callers
sk_psock_destroy_deferred(), is deferred after an RCU grace period and after
cancel_work_sync() so there should be no users to into the skb queue. If there
are we have other problems I think.
sk_psock_drop() is the other. It is called when the refcnt is zero and does
a sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED). Should it just wrap
up the clear_state and sk_psock_zap_ingress similar to other cases so it
doesn't have to deal with the case where enqueue happens after
sk_psock_zap_ingress.
Something like this would be clearer?
void sk_psock_drop(struct sock *sk, struct sk_psock *psock)
{
sk_psock_stop()
write_lock_bh(&sk->sk_callback_lock);
sk_psock_restore_proto(sk, psock);
rcu_assign_sk_user_data(sk, NULL);
if (psock->progs.stream_parser)
sk_psock_stop_strp(sk, psock);
else if (psock->progs.stream_verdict)
sk_psock_stop_verdict(sk, psock);
write_unlock_bh(&sk->sk_callback_lock);
call_rcu(&psock->rcu, sk_psock_destroy);
}
EXPORT_SYMBOL_GPL(sk_psock_drop)
Then sk_psock_zap_ingress, as coded above, is not really needed anywhere and
we just use the lockless variant, __sk_psock_zap_ingress(). WDYT, to I miss
something.
> }
>
> @@ -654,6 +655,17 @@ static void sk_psock_link_destroy(struct sk_psock *psock)
> }
> }
>
> +void sk_psock_stop(struct sk_psock *psock)
> +{
> + spin_lock_bh(&psock->ingress_lock);
> + sk_psock_clear_state(psock, SK_PSOCK_TX_ENABLED);
> + sk_psock_cork_free(psock);
> + __sk_psock_zap_ingress(psock);
> + spin_unlock_bh(&psock->ingress_lock);
> +
> + cancel_work_sync(&psock->work);
> +}
> +
> static void sk_psock_done_strp(struct sk_psock *psock);
